Increasing Stability of Crew Schedules in Airlines

In airline traffic disruptions occur frequently and cannot be totally avoided. They may lead to infeasible aircraft and crew schedules during the day of op-erations, due to absence of resources or violation of crew rules. The process of finding new schedules in such cases is called recovery or disruption manage-ment. The short-term recovery actions usually imply additional costs meaning that the total operational costs of a crew schedule can be significantly higher than the original planned costs. It is generally desirable to construct the sched-ule already in the planning phase in such a way that not just the planned costs, but the total operational costs are minimized. The goal is thus to construct schedules which remain feasible or can be recovered without high costs in cases of disturbances. This approach is generally called robust scheduling. There is no unique definition about robustness in airline scheduling. From our point of view it is important to realize that robustness involves the two aspects stability and flexibility. A schedule is stable if changes in operating en-vironment imply only small changes in the schedule. For example delays can t